Distribution.-South Orkneys, South Shetlands, Antarctic Peninsula, and Queen Maud Land, and the eastern margins of the Ross Sea. Living specimens were taken in 30-1116 m (Fig. 11).

We include records for this species re­ported from the area of Queen Maud Land (as C. elongata). Figured specimens from this region (Numanami, 1996:fig. 106A-B, E-F). appear to have weaker, more numer­ous spiral cords. One specimen from Syowa station has rachidian teeth with narrower cusps and additional serrations, features that had not previously been observed in spec­imens of C. signeyana. Powell (1951:142, fig. L78) reported and illustrated similar ad­ditional serrations in a specimen of Chlan­idota (Pfefferia) elata.

We have examined and also include re­cords from the eastern margin of the Ross Sea, which had been listed as Chlanidota cf. lamyi by Dell (1990:310). Dell (1990) noted that these broken and worn speci­mens closely resemble C. signeyana (as C. lamyi) from the South Shetland Islands, but differed only in having more numerous spi­ral cords on their body whorl.

Remarks.-Lamy (1910) was the first to recognize this species, proposing the taxon Cominella (Chlanidota) vestita var. elon­gata, without realizing that the name was preoccupied by Cominellaelongata Dun­ker, 1857. Powell (1951:141) considered Chlanidota elongata to be restricted to the South Shetland Islands and erected the taxon C. signeyana based on material from the South Orkney Islands. He recognized that C. signeyana was closely related to C. elon­gata, but distinguished it as being "con­stantly broader and of ovate rather than cy­lindrical outline." Cernohorsky (1977:110) noted that Cominella (Chlanidota) vestita var. elongata Lamy, 1910 was preoccupied, but questioned whether this taxon was dis­tinct from C. vestita. After examining a broader range of specimens than were available to Powell, Dell (1990:180) noted that both ovate and cylindrical phenotypes co-occurred in South Shetland and South Orkney samples, but that specimens could be sorted into one or the other phenotype on the basis of the ratio of shell width (SW) to shell height (SH). He regarded Chlani­dota signeyana to be limited to the ovate phenotype with SW/SH ratios ranging from 0.60 to 0.66 and proposed the new name Chlanidota lamyi (for Cominella elongata Lamy, 1910, non Dunker, 1857) for the elongate phenotype, with SW/SH ratios be­tween 0.55 and 0.60. He did, however, recognize the possibility that "these two forms are but extremes of the same species."

Dell (1990) also described C. pyriformis based on a single lot (11 specimens) collected off the South Shetland Islands, which he regarded to be a morphologically consistent shallow-water form allied to both C. signeyana and C. lamyi, but distinguished by its tapering, conical spire.

We examined and measured a large series of specimens from throughout the ranges of the three nominal species, but were unable to differentiate between them in any reproducible manner. Larger samples from sev­eral stations (e.g., USNM 901669, USNM 897557, USNM 860181) revealed that each population spans the range of morphologies of at least two, and sometimes all three of these nominal species. Chlanidota signey­ana is highly variable in shell outline and spiral sculpture, and encompasses the phe­notypes of Chlanidota lamyi and C. pyri­formis.

There does appear to be a clinal gradient in shell shape, with northern specimens tending to be more inflated, while popula­tions from the southern portion of the spe­cies' range, including the Antarctic main­land, have a higher proportion of narrower and more cylindrical shells. Numanami (1996:146) recognized a similar gradient in shell morphology in the taxon Neobuccin­urn eatoni, noting that specimens from the Kerguelen and South Shetland Islands tend­ed to be more elongated, while the samples from Enderby Land tended to be more in­flated and shorter spired. However, his large sample (n=98) from Enderby Land showed a wide variability in shell form, and included examples from the entire range of variation for the species.

Chlanidota signeyana is most similar to C. (C.) paucispiralis Powell, 1951, but differs in having more numerous and weaker spiral cords. Moreover, C. (C.) signeyana has not been recorded off South Georgia, while C. (C.) paucispiralis is endemic to South Georgia Island.